Kyson, just to be sure I understand, when you say “data leak” you only mean “data will no longer go through the VPN.” In other words, it reverts to being a normal router, allowing LAN to forward to WAN without using the VPN.

It seems there are (at least) two reasons people use a VPN:

  1. The user wants to do private Internet browsing and/or wants their browsing to originate at the VPN destination. They might be using a public VPN service. For this user, I can see how they would NOT want to go on the Internet without the VPN.

  2. The user needs to link two LAN networks across the Internet. This user probably controls the VPN server and client. Only the LAN traffic needs to be private so only the LAN traffic goes on the VPN. However this does not mean that LAN traffic will leak onto the Internet any more than if you use the router without the VPN feature.